Now Ms Bissett has posted comments on the Heart of Dunbar Facebook page after her son was criticised for joining in with the drinking game that has so far claimed two young lives in Ireland.

Locals in Dunbar took to the community page to claim youngsters in the town have been jumping into the harbour for fun for decades, and pointed out that hundreds took part in the town's annual Loony Dook on New Year's Day.

James Thomson wrote: "I was speaking to my mother about this and her reply was 'your father and his cronies used to jump off the bridge into the harbour after the pub on a Saturday night - and that was 60 years ago'."

David Black added: "I can't believe how many adults are condoning it. Maybe they should take a jump in the harbour in February."

But Ms Bissett, 44, hit back by replying: "Well there was a few done [it] on New Year's Day - it was a Loony Dook down the beach.

"I'm not defending a drinking craze, I don't even drink myself, but I am defending my son."

Ms Bissett added: "Sean has been jumping into the harbour since he was able to swim and is aware of the dangers, but thank you for your concern."

Following Bisset's dive into the harbour local parents and councillors branded him a "lunatic" and an "idiot" for risking his life in the freezing waters.

Dunbar councillor Paul McLellan, SNP, said: "This seems to have taken off across the country, but it is an incredibly stupid thing to do.

"I would urge everyone - especially youngsters - in Dunbar not to join in in this craze as it has already taken lives.

"The harbour at Dunbar is a working harbour and can be a dangerous place, never mind if the person has been drinking.

"By taking part in this they are putting, not just, their own lives in danger but other people's lives too if they have to jump in to save you. Please don't do it."

Dr Evelyn Gillan, chief executive of alcohol Focus Scotland, warned any type of drinking game could have "tragic consequences".

She said: "This craze sweeping social media is of serious concern. It encourages people to down drinks and then dare their friends to copy the trend.

"If we want tom protect our young people from the dangers of drinking to such an extreme excess we need to get rid of the cheap alcohol which is so widely available and heavily marketed."

Two men are thought to have died recently by taking part in the Neknomination craze. Jonny Byrne, 19, from Northern Ireland and Ross Cummings, 22, from Dublin, have both died in recent weeks after taking part in the drinking challenge.

Sean and Elaine Bisset have chosen not to comment further after being contacted yesterday.